Fenclofenac was shown to possess anti-inflammatory, antinociceptive and antipyretic properties as measured by tests in rats that detect clinically active compounds. In a chronic test for assessing anti-inflammatory activity (established adjuvant arthritis), it was approximately equipotent to alclofenac, fenoprofen calcium and phenylbutazone, more potent than acetylsalicylic acid and ibuprofen, but was less potent than diclofenac sodium, indomethacin, ketoprofen and naproxen. In contrast, the potency of fenclofenac in acute tests for anti-inflammatory, antinociceptive and anti-pyretic activity was generally lower, the drug being approximately equipotent to acetylsalicylic acid in such tests. The anti-inflammatory activity of fenclofenac was not mediated via the pituitary-adrenal axis or a counter-irritant action. Fenclofenac was shown to have remarkably low gastric ulcerogenic potential, both acutely and chronically.